1. Technical Field
The present disclosure is related to automotive radar systems and, in particular, to an apparatus and method for attenuating close-range radar signals in an automotive radar sensor.
2. Discussion of Related Art
In automotive radar systems, the radar sensor can be mounted, i.e., physically attached, to the vehicle body or frame. Alternatively, the sensor can be mounted to the bumper fascia. Radar system performance is typically characterized based on the ability of the automotive radar system to detect objects and correctly determine their range, bearing and Doppler velocity. For radar processing purposes, it is often preferred that the sensor be mounted to the bumper fascia instead of the vehicle frame or body. This is because, when the sensor is mounted to the fascia, radar system performance is typically better because the radar sensor and fascia vibrate together, i.e., they are synchronized and in phase. As a result, the radar sensor sees the fascia as being stationary, i.e., at a constant distance, with respect to the radar sensor. The fascia is processed by the radar as a constant signal. As such, the signal due to the return from the fascia can be easily removed from the radar signal before further processing.
Some automobile manufacturers, however, prefer that the radar sensor be mounted on the body to enhance ease of assembly, or for other reasons. In that configuration, i.e., with the radar sensor mounted on the body or frame, radar system performance can be degraded by vibration, since movement of the fascia is not synchronized to movement of the sensor. Instead of the constant fascia signal, movement of the fascia relative to the sensor due to vibration appears as a time-varying signal, which can be difficult to remove from the radar signal. Incomplete removal of the fascia signal degrades the ability of the radar to detect objects and/or correctly estimate object parameters.